Alkaline metal salts of .omega.-hydroxy-(.omega.-3)-ketoaliphatic acid represented by the general formula (5): ##STR1##
(wherein n is an integer of 7 to 13, and M indicates an alkaline metal), and .omega.-hydroxy-(.omega.-3)-ketoaliphatic acids represented by the general formula (10): ##STR2##
(wherein n is an integer of 7 to 13) are useful as a variety of synthetic raw materials and intermediates and are particularly important intermediates for macro cyclic lactone-based perfumes in the perfume industry.
2-(.omega.-Alkoxycarbonylalkanoyl)-4-butanolide is useful as a variety of synthetic raw materials and intermediates and is effectively used as an intermediate in the production of the above-mentioned .omega.-hydroxyaliphatic acid, which is a particularly important intermediate for large cyclic lactone-based perfumes, such as cyclopentadecanolide and cyclohexadecanolide, in the perfume industry.
Among conventional synthesizing processes for .omega.-hydroxyaliphatic acid, a method using .omega.-cyanoundecanoate ester and .gamma.-butyrolactone as starting materials is disclosed in Japanese Patent Application Laid-Open No. Hei 5-86013.
In this method, however, raw materials are generally difficult to prepare, and relatively expensive methyl 11-cyanoundecanoate is used as a raw material. Furthermore, ammonia formed in the final carboxylation step of the nitrile group at the .omega.-position requires a complicated procedure and adversely affects the scent of the final product; hence this method is still industrially unsatisfactory.
Other synthesizing methods for (.omega.-hydroxyaliphatic acid using .alpha.-(.omega.-cyanoalkanoyl)-.gamma.-butyrolactone as a starting material are disclosed in Japanese Patent Application Laid-Open Nos. 3-11036 and 5-86013. As an advantage of these methods, the intermediate, .omega.-hydroxyketonitrile, which is prepared by hydrolysis and decarboxylation of .alpha.-(.omega.-cyanoalkanoyl)-.gamma.-butyrolactone in the presence of an alkaline metal hydroxide, is oil-soluble; hence a large amount of water used and alkaline metal carbonate formed as a byproduct are easily separable.
Starting materials for .alpha.-(.omega.-cyanoalkanoyl)-.gamma.-butyrolactone, however, are difficult to obtain. When relatively expensive a .omega.-cyanoundecanoate ester is used as a raw material or when the nitrile group at the .omega.-position is finally carboxylated, ammonia forms. Thus, a complicated process is required and ammonia adversely affects the scent of the final product; hence, this method is still industrially unsatisfactory.
PCT Patent Application Laid-Open No. WO97-06156 discloses a method using a significantly readily obtainable and inexpensive dicarboxylate ester represented by the general formula ROOC(CH.sub.2).sub.n COOR, wherein n is an integer of 7 to 13 and R is an alkyl group, and .gamma.-butyrolactone as starting materials. In this method, an excess of dicarboxylate ester is mixed with .gamma.-butyrolactone in the presence of a basic condensing agent at room temperature and is heated and stirred under normal pressure while removing methanol formed in the reaction to prepare 2-(.omega.-alkoxycarbonylalkanoyl)-4-butanolide. This method is also excellent.
The selectivity and yield, however, is still unsatisfactory. Furthermore, a large excess of aqueous alkaline solution must be added during hydrolysis and decarboxylation of the intermediate, 2-(.omega.-alkoxycarbonylalkanoyl)-4-butanolide. Thus, a disadvantage of the method is removal of the large amount of water by distillation before the subsequent Wolff-Kishner reduction step.
In this method, an excess of dicarboxylate ester which is two times or more the fed amount of .gamma.-butyrolactone is used to increase the selectivity on the basis of the dicarboxylate ester raw material represented by the above-mentioned general formula, and unreacted dicarboxylate ester is recovered from the reaction mixture to reuse in the next reaction.
In the separation of the unreacted dicarboxylate ester and 2-(.omega.-alkoxycarbonylalkanoyl)-4-butanolide after the reaction, after acidification of the condensation solution, extraction with a solvent such as ethyl acetate, washing, and recovery of the solvent, the reaction mixture is subjected to simple distillation so that the unreacted dicarboxylate ester in the distilled section is separated from the condensation product, 2-(.omega.-alkoxycarbonylalkanoyl)-4-butanolide, in the distillation residue.
This method, however, requires a complicated process including many steps, such as extraction and simple distillation, and has a problem of decomposition of 2-(.omega.-alkoxycarbonylalkanoyl)-4-butanolide in the distillation. Furthermore, in the subsequent alkaline hydrolysis, decarboxylation, and Wolff-Kishner reduction, the method requires a complicated step in which alkaline is readded to 2-(.omega.-alkoxycarbonylalkanoyl)-4-butanolide obtained by the acidification.
Japanese Patent Application Laid-Open No. Hei 4-134047 discloses a method for separating three types of mixtures, that is, .omega.-hydroxyaliphatic acid or its ester, .alpha.-.omega.-diol, and dicarboxylic acid or its ester, but does not suggest a compound having a carbonyl group in the molecule.